Since Android is a Linux-based operating system for smartphones and tablets it shares the basic Linux "like" file system structure. Purists will argue that Linux is a kernel, not a file system structure, but people get the point. Android runs on top of a standard Linux kernel, and uses many of the same kernelspace utilities. The directory structure of Android looks similar to the directory structure of common Linux distributions. Android utilizes certain conventions providing uniformity in partitions versus directories on a partition. There are mainly 6 partitions in Android phones, tablets and other Android devices: boot, system, recovery, data, cache, misc.
Click on a folder for details on purpose.
device | +---acct +---cache +---config +---d +---data | +---app +---dev +---efs +---etc +---factory +---lib +---mnt | +---asec | +---extSdCard | +---obb | +---sdcard | | +DCIM | +---secure | +---UsbDriveA | +---UsbDriveB | +---UsbDriveC | +---UsbDriveD | +---UsbDriveE | +---UsbDriveF +---preload +---proc +---root +---sbin +---sdcard +---storage +---sys +---system | +---app | +---bin | +---cameradata | +---csc | +---etc | +---fonts | +---framework | +---hdic | +---lib | +---media | +---T9DB | +---tts | +---usr | +---vendor | +---vsc | +---wallpaper | +---xbin +---vendor